Clean the chicken: Remove all the giblets, trim, and pat the chicken dry.
Stuff the chicken with the onion and garlic cloves. Tie chicken legs together with kitchen thread.
In a small bowl, mix the seasonings and melted butter. Rub this mixture all over the entire chicken. You can use a basting brush to make this a cleaner process.
To Cook the Chicken: Heat your grill to high heat on one side. You want the temperature inside your grill to be about 375 degrees. To barbecue the chicken, we will be using indirect heat. Place chicken on the barbecue with the legs facing the back of the barbecue on the opposite side of the heat. Close the lid and let cook for 45 minutes and do not open.
Rotate the chicken so the wings are facing the back of the barbecue and close the lid. Let cook for another 40 minutes. Internal temperature of the chicken should be 165 degrees.
Once your chicken reaches an internal temperature of 165 degrees, it is ready to come off the grill. Let the chicken rest for about five minutes. Carve your chicken and serve warm.